Such fluid actuators are fundamentally known for influencing the flow along a flow surface of a flow body, for example. Such fluid actuators are utilized, e.g., in order to cause flows to adhere longer along a flow body, or to reattach a flow that has detached or separated from a flow body to the latter. This is expedient and advantageous, for example, when the known fluid actuators are employed with flow bodies having the form of adjustable flaps, control flaps, or other parts of a wing of an aircraft.
In order to reattach flows that have already separated to a flow body, it is known to realize the fluid actuators in such a way that a pulse-type ejection from the openings of a fluid actuator takes place. Pulse-type ejection of fluid from the openings of a fluid actuator has the consequence of a previously detached flow being reattached to the top side of the flow body by causing the ejected fluid flow to become turbulent. In other words, energy-rich flow spaced apart from the flow body is approached to the flow body again and thus reattached to the flow body.
In order to enable the pulse-type ejection of the fluid, it is already known that openings corresponding to each other, for instance pairs of openings of a fluid actuator, cooperate in such a manner that a fluid pulse and thus an abrupt outflow of the fluid, alternatingly takes place through these openings. In this way, starting out from a continuous fluid flow a distribution to two openings—i.e. a pair of openings—of a fluid actuator may take place so that an uninterrupted, continuous fluid flow may be utilized for creating a pulse-type ejection. The known fluid actuators utilize valves for the distribution between the two openings of the fluid actuator. Such valves include a multiplicity of mechanical components which must be movable for switching back and forth between the two outlet openings of the fluid actuator. These mechanical components and thus the valves are correspondingly subjected to high mechanical strains in dependency on the frequency of the pulsation between the two outlet openings of the fluid body. Due to these high mechanical strains the valves are expendable parts that have to be replaced at comparatively short-term intervals on the one hand, while on the other hand their required functionality has to be examined at even shorter intervals. The risk of a failure of such valves accordingly is a problem that is problematic in regard of the approval of such a fluid actuator in aviation. In addition, the individual mechanical components of the valve result in a relatively complex construction that brings about high manufacturing costs because of a multiplicity of individual parts. Aside from high costs, the mass of the parts and the complexity of the construction moreover result in an increased weight, which is a drawback in the case of aircraft on account of the concurrently increased fuel consumption.
From U.S. Pat. Nos. 3,504,391 and 3,528,442 fluid actuators are known which comprise a control stage and a single end stage connected to this control stage. The control stages comprise two outlet passages, each of which has a feedback line associated thereto. The outlet passages merge into a chamber which is in connection with the end stage for the purpose of driving the latter.
From DE 60 2006 001 040 T2 a fluidic oscillator is known which comprises a plurality of oscillator elements arranged adjacently side by side along a wing span extension direction of an aircraft wing. To each oscillator element two feedback lines are associated, both of which are connected to feedback lines of the respective oscillator elements immediately adjacent thereto.